1. Field of the Invention
The present invention relates to a manipulation-protected foil structure and a method for its manufacture.
2. The Prior Art
Many applications of self-adhesive foils or labels require precautions which prevent the foil or label from becoming detached from the object to which it was originally attached, and wrongly stuck on another object. This particularly applies to self-adhesive identification plates, for example, for the unique identification of products or for product protection.
In order to make the misuse of such foils more difficult, hitherto a relatively unstable foil material was frequently selected and the adhesive bond to the base was constructed as so strong that the foil tears when an attempt is made to detach it intact from the base. However, the mechanically less stable foils required for this purpose are generally more expensive than more tear-proof foil material.
A so-called repositionability of the foil or of the labels made from the foil is frequently required by the user. By this is understood the possibility of removing and being able to re-position the foil or the label stuck onto an object within a certain time after application, possibly to correct an incorrect position or orientation. Only after this time should such a foil or such a label be no longer detachable intact. This repositionability cannot be achieved with the known mechanically weak foil material which already has an imminent tendency to tear.
A further known measure for making it difficult to detach foils or labels intact consists in providing lines of weakening in the foil. Lines of weakening are subsequently also to be understood as lines of interruption i.e., lines along whose profile a foil or foil layer is cut through its total thickness. Lines of weakening are usually stamping or punching lines but can also be executed as cuts, perforations, scoring or the like. In the stuck-on state, the lines of weakening prevent the complete foil or the complete label from being removed since this tears into individual parts along the lines of weakening or starting therefrom. The individual parts cannot be joined together again or only at great expense.
If the lines of weakening inside a label run continuously from edge to edge, there is the problem that it is difficult to dispense the label since the part regions of the label formed by the lines of weakening are only weakly held together, for example, by the non-co-weakened adhesive layer of the label, between the dispensing from the label supporting web made of pull-off material and the adhesion onto the object as intended. Such labels are the usual standard for-price marking in supermarkets. In order to increase the stability of the label during dispensing, the lines of weakening can be interrupted by cross-pieces whereby the foil stays cohesive. However, this usually only works with selected geometries of label and arrangement of lines of weakening and because labels are usually punched out of cohesive material webs which are provided with lines of weakening before the punching process. If the punching position of the labels is unfavorable relative to the lines of weakening, larger regions, for example, at the corners of a label, can be separated from the remainder of the label by a line of weakening.
The label structure known from the German Utility Model DE 299 13 746 U1 attempts to counteract these difficulties, whereby in addition to a layer provided with lines of weakening and an adhesive layer for fixing to a base, there is also provided a continuous upper foil which is affixed by means of adhesive to the layer provided with lines of weakening. The upper foil holds the layer together and ensures that the label is repositionable. Moreover, there is thus a smooth and therefore high-resolution printable surface. When such a structure is realized using cheap, mechanically relatively stable foils however, the problem again arises that the upper foil can be pulled off and stuck onto another object. The protection against manipulation originally strived for by the lines of weakening is thus no longer fully guaranteed.
However, labels and foils not only of the aforesaid type are generally inscribed or must be inscribed, frequently individually. Sometimes, laser inscription methods are used here. In this case, a laser-sensitive layer in the foil structure to be inscribed locally changes its color as a result of laser irradiation or is locally ablated by the laser action. The inscription is produced by moving the laser along the desired sign contours. In the latter case, the laser-sensitive layer can lie under a laser-transparent laminate so that the removed particles do not enter the atmosphere. Such a structure is described, among other thing in the German Patent Specification DE 196 42 040 C1. However, the laser-sensitive layer can also be constructed as the uppermost layer of the foil structure so that the particles are released.